Long-term objectives: Describe the anatomical variations of the vasculature of primate retinas, with special emphasis on the fovea. Relate the geometry of the vasculature to the structure of the neural layers. Compare the chacteristics of the vascular patterns at different retinal loci. Specific Aims: Study the retinal vasculature of primate retinas in histological preparations. Describe the laminationof retinal capillaries and their relationships to the planes established by the neural layers. Compare the capillary planes to planes of high metabolic activity. Build solid models of the vascular networks using computer image analysis techniques to obtain a three- dimensional view of the interconnections betwee the capillary planes at selected retinal loci. Determine which anatomical features of the vasculature are readily observed in vivo by fluorescein angiography. Characterize unusual patterns of the foveal vasculature, such as vessels crossing the foveola and relate them to any concomitant anatomical anomalies of the retina. Methods: Monkeys will be studied by fuundus photography and fluorescein angiography. Retinas from the same animals will be prepared as whole mounts and a continuity diagram of the vessels will be drawn at high magnification. The depth planes of the vessesl will be coded on the drawings and enterd into an image analysis systems to build a three-dimensional model. The retinas will be sectioned to relate the vessel planes to the neuronal bujndary planes and planes of high cyutochrome oxidase activity. The detail available in the histological preparations will be compared with fundus photos and fluorescein angiograms. Significance and Helath Relatedness: The literature on the retinal vasculature, particularly in the fovea, is full of contradictions and errors. By relating the vasculature to the neural layers, many of the issues can be resolved. It will then be possible to interpret clincial tests such as fluorescein angiograms with more confidence and precision. The results may assist in understanding the changes in the retina that occur in patients with diabetes, macular degeneration, and other conditions.